Metal-cutting tool



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Pun/in B. R. PuRvlN Y METAL CUTTINGTQOL Filed-sept. s, 1958 Aug. 29, 1944.

9 sheets-sheet 9 INVENTOR Belga min R. Puri/in A TORNEY Patented Aug. 29, 1944 METAL-CUTTING TOOL Benjamn R. Purvin, Rockford, Ill., assignor to Barber-Colman Company, Rockford, Ill., a' corporation of Illinois Application September 3, 1938, Serial No. 228,312

22 Claims.

The present invention relates to improvements in machine tools, and has particular reference to a new and improved metal cutting machine, of the type disclosed in my copending application Serial No. 75,949, led April 23, 1936, now Patent Number 2,167,267, issued July 25, 1939, adapted for hobbing spur'gears, helical gears, spur and spiral spline shafts, and other symmetrical forms capable of being hobbed.

One of the important objects of the present invention is to provide a novel bobbing machine which results in the tool having a ,greatly increased life, which has a high rate of production because of improved means for supporting the hob and the work and increased hob `speeds and cutting feeds, which accurately maintains close tolerances and produces an improved finish, which has an infinitely variable range of feeds from Zero to maximum, which is simple and easy to operate, and which is compact, rigid and sturdy in construction.

Another object is to provide a new andimproved hobbing machine which is automatic in operation, and in which the primary movements of the tool and work and the actuation of various clamping devices are obtained by hydraulic power, thereby reducing and lightening the manual labor required in the set-up and control of the machine.

A further object is to provide a novel automatic hobbing machine having a work spindle and a hob spindle relatively translatable axially of the work spindle, and having cycle control means selectively adjustable to obtain a conventional cycle in which the spindle translation comprises a feeding movement in one direction, automatic reversal, a rapid traverse movement in the other direction and an automatic stop, or a climb cutting cycle in which the aforesaid movements are reversed, or either of the foregoing cycles with an automatic stop at the end of the feed movement.

Another object is to provide a new and improved hobbing machine having a spindle slide movable selectively into an inoperative position or an operative position, and means for automatically clamping the slide in operative position.

A further object is to provide a novel hobbing machine having a base with a vertical column, a tool spindle slide on the base, a work spindle slide on the column, adjustable stop means for limiting the movement of the Work spindle slide either into a lowered operative position or into an elevated inoperative position, and hydraulic means for slide.

Another object is to provide a novel hobbing machine comprising work and tool spindles, means for rotating the spindles in timed relation including a differential mechanism for varying the relation, a selective mechanical rapid traverse and feed drive for effecting relative translation between the spindles and operation of the differential fmechanism, and a selective rapid traverse and feed hydraulic transmission for actuating the mechanical drive.

A further object is to provide novel means for preventing translation of the tool spindle slide unless the work and tool spindle are rotating.

Further objects and advantages will become apparent as the description proceeds.

In the accompanying drawings,

Figure 1 is a front elevational view of a hobbing machine embodying the features of my invention.

Fig. 2 is a plan View of the machine.

Fig. 3 is a diagrammatic representation of the drive for the machine, and particularly the hydraulic transmission. V

Fig. 4 is a left end view of the machine, partially in section along line 4 4 of Fig. 7.

Fig. 5 is a fragmentary detail sectional view of the feed adjustment control taken along line 5-5 of Fig. 1.

Fig. 6 is a sectional view taken along line 6 6 O Fig. 5.

Fig, 1la is an enlarged view of the back pressure valve illustrated in Fig. 3. f I

Fig. 11b is an enlarged view of the start and stop valve illustrated in Fig. 3. Y

Fig. 12 is a horizontal sectional view of the valve control unit, Y v

Fig. 13 is a vertical sectional View of the valve control unit taken substantially along line l3-l 3 of Fig. 12.

Fig. 14 is a detail sectional view taken substantially along line lll- I4 of Fig'. 13.

Figs. 15 and 16 are vertical sectional views of elevating and lowering the tool spindle the valve control unit taken respectively along lines I5-I5 and I6-I6 of Fig. 12.

Fig. 17 is a horizontal sectional View of the valve control unit taken substantially along line II-I1 of Fig. 13.

Fig. 18 is a, detail view of means for controlling the clutch valve.

Fig. 19 is a sectional view on an enlarged scale of the Work slide clamping means.

Fig. 20 is a fragmentary Vertical sectional View taken along line 2li-20 of Fig. 19.

Fig. 21 is a fragmentary sectional view taken along line 2 I-2I of Fig. 2, and illustrating means for adjusting and positioning the work slide.

The hobbing machine constituting the exemplary embodiment of the invention comprises a hollow base which consists of a horizontal bed I having a low platform 2 at thev rear, and opposite end pedestals 3 and 4. Two upright columns 5 and 6 are rigidly mounted respectively -on the pedestals 3 and 4.

A work slide 1 is mounted for vertical positioning on double V ways 8 formed on the front of the column 5, and has an integral over-arm 9 guided on flat ways I Il on the front of the column 6. Journaled in the slide 1 is a hollow work spindle II adapted to be connected to one end of a Work arbor I2 supporting a gear blank W. The other end of the arbor I2 is adapted to be supported by an outboard support or tailstock I3 mounted for adjustment onlongitudinal dovetail ways I4 on the underside of the over-arm 9. The tailstock I3 may be adjusted along the ways I4 by gear means (not shown) having an operating lever I5, and may be clamped in position by a clamp (not shown) having an operating lever I6.

A hob slide I1 is mounted on V and at ways I8 on the top ofthe bed II for travel axially of the spindle I I. A swivel plateY I9 is mounted on the slide I1 for angular adjustment about a vertical axis, and is formed with a Vdiametrical guide- ,way 20 adjustably supporting a spindle slide 2l.

Journaled in the slide 2| is a spindle 22 adapted to support a cutting tool or hob T.

The Ywork slide The work slide 1 is movable hydraulically either into an elevated inoperative position or a lc-wered operative position, and is adapted to be clamped hydraulically in the operative position. These positions are defined by a non-rotatable vertical screw 23 (see Fig. 21) threaded through a rotary nut 24 journaled in a lug`25 on the rear of the slide 1 between the ways 8. The upper end of the screw 23 carries an abutment plate 26 adapted'for engagement with the underside of a forwardly projecting lug 21 on the column 5 to define the inoperative position, and has an axial extension 28 of reduced diameter extending slidably through the lug. The lower end of the screw 23 is splined for axial movement through a lug 29 on the rear and adjacent the bottom of the slide 1, and is adapted for engagement with a positive stop 30 on the bed I to define theoperative position. The screw 23 is vertically adjustable relative to the work slide 1 to establish precisely the desired depth of cut. Thus, a spiral gear 3l coaxial and rigid with the lower end of the nut 24 meshes with a spiral pinion 32 fixed 'on the inner end of a shaft33 journaled inthe slide 1 and extending therethrough to the front of the machine. A micrometer dial 34 is xed on the front end of the shaft 33 to indicate the depth adjustment. A locking screw 35 `is threaded through the slide 'I for engagement with the periphery of the nut 24 to secure the stop scrw' 23 releasably in position.

Vertical movement of the Work slide 'I between the limit positions is obtained by a hydraulic cylinder and piston motor 36 (see Figs. 3 and 4) rigidly mounted on the floor of the pedestal 3 and having a vertical piston rod 31 extending upwardly into operative engagement with the bottom of the slide body.

The work slide 1 is confined for vertical movement against the Ways 8 by suitable gib plates 38 (see Figs. 19 and 20) bolted in position. Adjustably mounted in the plates 38 are suitable tapered gibs 39 engaging rear clamping surfaces 40 on the ways 8. A plurality of hydraulically operable clamps 4I, four in the present instance and located respectively adjacent the ends of the gib plates 38, are arranged to coact with the gibs 39 to secure the Slide 1 rigidly in operative position. These clamps preferably are alike in construction, and hence a description of one will suffice for all.

Each of the clamps 4I comprises a cylindrical plunger 42 which is slidable in a transverse bore 43 opening to the front of the work slide 1, and which intermediate its ends is formed with a longitudinal diametrical slot 44. The rear end of the plunger 42 has an axial stem 45 which extends slidably through a bore 46 to the rear of the work slide 1, and then freely through a transverse notch 41 in the inner face of the gib plate 38 and a bore 48 opening from the notch to the rear of the gib plate. A clamping block 49 is slidably disposed on the stem 45 within the notch 41, and is formed in oneend with a notch 50 intertting with and engaging the taper gib 39. A collar 5I is slidably disposed on the stem 45 within the bore 48, and is conned against the rear of the block 49 by two lock nuts 52, whereby the block may be adjusted relative to the plunger 42.

Extending transversely through the slot 44 is a wedge member 53 in the form of a flat tapered bar adapted to impart a forward thrust to the plunger 42 to apply the clamp block 49. The wedge bar 53 is in anti-friction bearing engagement at opposite sides with two rollers 54 disposed within the slot 44. One of the rollers 54 bears against a hardened block-55 removably secured by a screw 56 against the forward end of the slot 44. The other roller 54 bears against the forward edge 51 of a hardened pin .58 extending transversely through the bore 43 and the slot 44. The pin'58- is inserted in a transverse bore 58a in the side of the work slide 1, and is flattened to intert slidably with the slot 44, thereby restraining the plunger 42 against rotation.

The wedge bar 53 extends into the bore `43 from the interior of the work slide 1 through a transverse bore 59 closed at the outer end by a cap 60, and is rigidly connected at the inner end to a pistonl 6I reciprocable in a hydraulic vcylinder 462 adapted to receive pressure fluid. A coiled compression spring 63 engaging the piston 6I tends to retract the bar 53. It Will be understood that when pressure fluid is supplied to the cylinder`62, the bar 53 will be forced outwardly, and through the rollers 54 rolling on the block 55 and the pin 58 will impart a powerful clamping thrust to the plunger 42.

The pistons 6I for the two upper clamps, and also the pistons for the two lower clamps, in each instance, are disposed in opposite ends of one cylinder 62. In addition to the four clamps for the work slide, a similar hydraulically operable clamp v61| is provided for securing the overarm 9 to the face of the column 6. This clamp comprises a headed bolt -65 movable in a vertical u Spindle drives The work and hob spindles I and 22 are rotated in timed relation from an electric drive motor' 61 mounted on the rear platform 2 of the machine. The motor 61 is connected through a flexible coupling 68 (see Fig. '1) to a shaft 69 journaled in a clutch housing 10 on the side of the pedestal A3. A gear 1| fixed on the shaft 69 meshes with a gear 12 on one end of a tubular shaft 13 which is journaled in a bearing 14 on the inner wall of the housing 10, and which is connected through a hydraulically operable clutch 15 to a coaxial shaft 16 extending through the pedestal 3 and journaled at opposite ends in bearings 11 and 18.

The clutch 15 may be provided in various forms, and as herein shown comprises an axially floating annular friction disk 19 splined for rotation with the gear 12, and disposed between two friction disks 80 and 8| splined on the shaft 16 within the housing 10. The outer end disk 80 is located in a fixed axial position against the bearing 18, and

lapping meshing engagement.

any position of adjustment or feed as more fully disclosed in my aforesaid copending application.

The rotative drive for the work spindle ll'is taken from a shaft |05 on which the intermediate gear |02 is fixed, and which is connected through a differential mechanism |06 to an axially aligned shaft |01. In the form shown, the differential mechanism |06 comprises a cage |08 rotatable about the shafts |05 and |01, and carrying a plurality of annularly arranged pinions |09 and ||0. These pinions are in endwise over- Inlet and outlet gears and ||2 are fixed respectively on the adjacent ends of the shafts |05 and |01, and mesh respectively with the pinions |09 and H0. Rigid with the cage |08 is a coaxial worm wheel ||3 which meshes with a Worm ||4 on a shaft ||5 l retard the rotation of the work spindle relative the other end disk 8| is movable axially to open and close the clutch 15. Suitable compression springs 82 are disposed between and tend to separate the disks 80 and 8| to release the intermediate disk 19. An actuating sleeve 83 is slidable on the shaft 16 and extends through the tubular shaft 13 for abutment at one end with the movable disk 8|. The other end of the sleeve 83 is engaged by an annular piston 84 reciprocable on the shaft 16 and within an encircling cylinder 85 fixed thereon. Formed in the shaft 1'6 is an axial passage 86 opening at one end through radial ports 81 to the closed end of the cylinder 85, and at the other end through radial ports 88 to the interior of a sleeve 89, closely encircling the Vshaft and rigid with a valve bracket 90, for connection to a source of pressure fluid. The sleeve 89 is formed with an internal annular groove 9| open to a fluid supply line 92 connected to the bracket 90, and adapted for communication with the ports 88. The sleeve 89 and bracket 90 assembly is supported on the shaft 1-6, and is held against rotation therewith by means of a lu-g 93 (see Fig 4) engaging the internal wall structure of the pedestal 3. Two adjusting screws 94 threaded through spaced lugs 95 on the bracket 90 into engagement with opposite sides of a fixed lug 96 serve to locate the bracket axially so as to obtain proper registration of the groove 9| with the ports 88. The supply of pressure fluid to the cylinder 85 will cause the driving disk 19 to be clamped frictionally between the driven disks 80 and 8|, thereby completing the drive to the shaft 16.

The shaft 16 (see Figs. 4, 7, and 8) extends through the bearing 11 into a gear box 91 on the outer end of the pedestal 3, and is therein connected through two change gears 98 and 99 to a parallel shaft |00. This shaft is connected through three change gears |0|, |02, and |03 to one end of a hob drive shaft |04 which extends longitudinally through the machine bed and is to the tool spindle 22 in timed relation to the movement of the tool slide |1.

The outlet shaft |01 of the differential mechanism |06 is connected through a train of speed- Vchange gears H5 to H9 in the gear box 91 to tubular enlargement |28 integral with one side suitably connected to drive the hob spindle 22 in 76 of the housing |24. A worm |29 on the shaft |21 meshes with a worm wheel |30 on the work spindle to complete the spindle drive.

The worm |29 is adustable relative to the Worm wheel |30 to take up backlash. In the present instance, the internal gear |25 is journaled in the lower end of the housing enlargement |28 coaxially with a rotatably adjustable bearing sleeve |3|, and the worm shaft |21 is journaled eccentrically in the sleeve for bodily movement toward and from the worm wheel |30 upon rotation of the sleeve to vary the depth of tooth engagement. An adjusting screw |32 is threaded tangentially into the bore of the housing enlargement |28 for engagement with a peripherally facing shoulder |33 formed in one side of the bearing sleeve |3|, and is manually adjustable to rotate the sleeve so as to shift the worm |29 through an arcuate path substantially normal to the spindle axis.

The hebl feed drive`V The hob T is adapted to be fed axially of the work spindle selectively at a rapid rate or a The..

transmission comprises a constant displacement reversible rotary hydraulic motor |34 adapted for connection by a system of hydraulic control circuits with a pump unit |35 as a source of motive fluid. The motor |34 and the pump unit |35 constitute part of a hydraulic f-eed unit (see-Figs. 8 and 1l) mounted on the inside of aremovable panel |36 in the rear wall of the pedestal-3.

The motor |34 is adapted to be connected to a transmission shaft 31, journaled at opposite ends in a clutch housing |38 on the panel |36, either through a rapid traverse drive or a feed drive. In the present instance, the rapid traverse drive comprises a gear |39 which is connected through an intermediate gear |40 on a shaft |4| t0 a gear |42 on the motor shaft |43, and which is journaled for rotation on the shaft |31 and adapted to be connected thereto by a rapid traverse one-way friction-clutch |44 operable by a clutch yoke |45. The feed drive is taken from the shaft |4|, and comprises a worm |46 thereon meshing with a worm wheel |41 on a transverse shaft |48 in the housing |38. A bevel gear |49 fixed on the shaft |48 meshes with a bevel gear |50 journaled for rotation on the shaft |31 and adapted to be connected thereto by a positive feed clutch The clutch |5| comprises a sleeve |52 splined on the shaft |31 for axial movement by a yoke |53, and having end teeth |54 movable into and out of engagement with complementary teeth |55 on the hub of the gear |50.

The two clutch yokes |45 and |53 are rigidly connected, for joini-l movement, to an actuating plunger |56 (see Figs. 3 and 4) reciprocable at opposite ends respectively in two hydraulic cylinders |51 and |58 adapted to be alternately supplied with pressure fluid.

The transmission shaft |31 extends from the clutch housing |38 through a worm housing |59 into a lead gear box |60 on the front of the pedestal 3. A worm |6| iixed on the shaft |31 within the housing |59 meshes with a worm wheel |62 on a drive shaft |63 journaled in and eX- tending longitudinally through the bed `and having a nut and screw unit drive connection (see Fig. 3) with the hob slide |1 as more fully illustrated in my said copending application.

The transmission shaft |31 is also adapted for connection through lead change gears |64 to |61 in the gear box |60 to the shaft ||5 for driving the worm 4 of the differential mechanism |06 so as to advance or retard the rotation of the work spindle in accordance with the feed of the hob slide |1 to compensate for the lead of the teeth when cutting spiral gears.

H ydraulz'c system Pressure fluid is supplied by the pump unit which is driven by the electric motor 61 from the shaft 69 through gears |68 and |69, and which consists of a variable deliveryfeed pump |10 and a rapid traverse pump |1| for supplying motive fluid to the hydraulic motor 34, and a gear pump |12 providing an auxiliary source of fluid for actuating the accessory elementsof the machine.

The variable delivery feed pump |10 is shown as of the piston and cylinder type having an actuating wobble plate |13 with an adjustable throw, and having an inlet line |14 and a pressure outlet line |15. The outlet line |15 is adapted to be connected through a start `and stop valve |16 to a sump or supply tank 11. T-he wobble plate |13 is operatively mounted against one end of a plunger '|18 slidable in a' hydraulic cylinder |19, and is axially adjustable to effect a. variation in the degree of eccentricity or angularity. An annular end face cam |80 is rotatably adjustable on the cylinder- |19, and is adapted for engagement With opposite ends-of a diametrical pin |8| extending through the plunger |18 to define the adjustment of the Wobble plate |13.

The cam |80 is manually adjustable to vary the pump displacement for different rates of feed, and to this end is integral with a ring gear |82 meshing with a worm |83 on a shaft |84. This shaft is connected through a universal joint |85 to a shaft |86 in turn connected through a universal joint |81 to a feed control shaft |88 journaled in and extending through the gear box |60 to the front of the machine. A hand knob |89 (see Figs. 4 to 6) is keyed to the shaft |88, and confines a concentric cylindrical graduated dial |90 rotatably against an indicator plate |9| on the front of the case |60. A central gear |92 on the hub of the knob |89 is connected through a train of gears |93 and `|94 to an internal gear |95 integral with the dial |90. The gear ratio is such that three revolutions of the knob |89 will effect one revolution of the control dial |90 for the complete range of feed adjustments. To facilitate ease of manual adjustment of the pump |10 during operation, the reaction of the back pressure of the pump on the plunger |18 is partially balanced or offset by directing fluid from the outlet line |15 to the outer end of the cylinder |19.

The rapid traverse pump |1| has an inlet line |96 opening from the sump |11, and discharges to the inlet line |14 of the feed pump |10. The gear Ypump 12 has an inlet line |91 opening from the sump |11, and an auxiliary pressure discharge line |98.

The start and stop valve |16 (see Figs. 3 and 11b) comprises a casing |99 formed in one end with a relatively small valve bore 200 and in the other end with a larger'valve bore 20|. Two pressure control lines 202 and 203 open respectively toopposite Aends of the bore 20|, and are adapted selectively to be blocked off or connected to exhaust as will be more fully described hereinafter. A centrally apertured stop disk 204 is positioned against the inner end of the bore 20|,

and constitutes a partition between the two bores 200 and 20|. Mounted in xed position in the center of the bore 20| is a plug 205 having an axial valve passage 206, and defining annular valve seats 201 and 208 at opposite ends. Two valve disks 209 and 2|0 are slidably disposed in opposite ends of the bore 20| for engagement respectively with the seats 201 and 208. These valve vdisks have a close sliding t with the bore 20|, and each is formed with a restricted aperture '2|'|. Coil compression springs 2|2 and 2|3 disposed in opposite ends of the bore 20| tend to seat the 'valve disks 209 and 2|0 with a predetermined spring pressure. Formed in the periphery of the bore 29| are two spaced ports 2|'4 and 2|5 connected tothe pump inlet line |14, and opening about the valve seats 201 and 208 for communication ,with the passage 206 when the valve disks 209 and 2|0 are lifted. The passage 206 exhausts through an intermediate port 2|6 tothe sump |11. The bore 200 opens at diametrically opposed points to the pump discharge line |15 and the sump. A valve plunger ,2|1' is reciprocable in the bore 200, vand is ,normally urged by a compression spring 2|'8 against the stop vdisk 204. 'The plunger v2`|`| is Vopens to an annular groove 236 in the bore 230 formed with ports 2|9 adapted in one position to relieve the pump outlet line to the sump |11.

In operation, when the line 202 is open to exhaust, pressure uid from the port 2 4 bleeding through the aperture 2|| in the valve disk 209 Will be dissipated so that there is no pressure in the inner end of the bore As a result, the plunger 2|1 will be positioned against the stop disk 204, thereby relieving the pressure line |15 to the sump, and the valve disk 200 will lift to partially relieve the inlet line |14 to the exhaust passage 266. If the control line 202 is blocked, pressure uid from the port 2|4 bleeding through the aperture 2|| in the disk 209 will build up pressure in the inner end of the bore 20|, but

from the port 2|5 bleeding through the aperture 2|| in the valve disk 2|0 into the outer end of the bore 20| will be dissipated. However, the pressure acting on the inner face of the valve disk 2|0 will tend to lift the disk from the seat I 208, thereby discharging part of the delivery of the rapid traverse pump |1I past the seat into the exhaust passage 206, and making available at the feed pump |10 fluid at a predetermined inlet pressure. As a result, pressure fluid will be supplied by the pump |10 to the line |15 at a feeding rate. If both control lines 202 and 203 are blocked, pressure will build up in opposite ends of the bore 20| to maintain both disks 208 and 2|0 in closed position, therebycausing the full delivery of the rapid traverse pump |1| to pass through the feed pump |10 regardless of the pumping action of the latter. As a result, pressure fluid will be supplied to the line |15 at a rapid traverse rate.

The discharge line |15 of the pump |10 is adapted to be connected through a direction control valve 220 'selectively to either of two supply lines 22| and 222 leading respectively to opposite sides of the hydraulic motor |34. The valve comprises a casing 223 having a cylindrical chamber 224 and a spool piston 225 reciprocable therein. In one end position of the piston 225, the pump line |15 is connected to the motor line 22|, and the line 222 is connected to an exhaust line 226 leading to a back pressure valve 221 discharging through a line 228 to the sump |11. As a result, the motor |34 will operate in a direction to traverse the tool slide to the left. In the other end position of the piston 225, the motor lines 22! and 222 are connected respectively to the lines 226 and |15 to reverse the operation of the motor |34.

The back pressure valve 221 (see Figs. 3 and 11) comprises a casing 229 having a bore 230 one end of which is closed and connected to a branch of the pump line |15 and the other end of which opens past a valve seat 23| to a chamber 232 exhausting to the line 228. A valve piston 233 is slidable inthe bore 230, and has a valve member 234 on one end adapted for engagement with the seat 23|. Suitable spring means 235 in the chamber 232 acts against the piston 233 in a direction to seat the member 234 against the pressure of the fluid in the closed end of the bore 230. The line 226 from the direction'valve 220 adapted for connection to the valve seat 23| when the valve member,l 234 is in or near closed position. Normally, the valve member 234 tends to block the line 226. If the back pressure exceeds a predetermined amount, it Will be reflected in the pumpr pressure which will lift the valve member 234. Consequently, a substantially constant back pressure will be maintained r'egardless of variations in cutting resistance.

An annular stop disk 231 is confined by a spring 238 in spaced position for engagement by the'piston 233 to limit the maximum normal opening movement of the valve member 234. i p

The piston 233is formed with an axial bore 239 one end of which opens to the chamber 232, and the other end of which connects with radial passages 240 movable into communication with an annular groove 24| in thevalve bore 230, connected toa branch of the pump line |15, when the valve member 234 lifts against the action of the spring 238. If the pump pressure rises substantially above a predetermined desired maximum, the line |15 will be relieved directly through the groove 24|, the passages 240 and the bore 230 to the exhaust chamber 232.

Preferably, the pumps |10, |1|, and |12 and the valves |16, 220, and 221 areY incorporated in a self-contained structure constituting the pump unit |35. The direction valve 220 is controlled by a pilot valve 242 operable in conjunction with a feed control'valve 243, or controlled by a rapid traverse valve 244. These valves form part of a selfcontained control unit 2'45 having a housing 246 mounted on the frontV of the machine. The housing 246 is closed vby upper and lower covers 241 and 248, and is formed with an inner mounting panel 240.' A valve block 250'is bolted to the panel 249, and coacts therewith to define various passages and lines of the hydraulic circuits.

vThe pilot valve 242 l(see Figs.4 16 and 11) comprises avertical bore 25| opening through the block 250 and closed at opposite ends by screw plugs 252. Formed in the bore 25| are five annular ports 253, 254,v 255, 256, and 251 of which the end ports 253 and 251 are connected to an exhaust line 258 draining to the sump |11. The center port 255 is connected'to the auxiliary pressure line |08, and the ports 254 and 256 are connected respectively tol two lines 250 and26|| leading to the feed contro1 valve 243. A valve piston 26| of the spool'type is slidable in the bore 25|, and has an axial stem 262 extending through the lower end plug 252 for selective manual actuation. 'Ihe end of the stem 262 is connected through parallel links 263 to a crank arm 264 fixed on a rock shaft 265 journaled in and extending through a bearing 266 in the cover 248. 'A hand lever 261 is fixed on the outer end.

`of the shaft 265, and is adapted to be locked in either of two operative positions by a manuallyreleasable spring-actuated detent pin 268 normally movable into suitably located recesses 260 in the front of the cover 248. The piston 26| serves in one end position to connect the lines Y plate21|p The ports 213 and 215 are connected to the passages 260 and 259, and the ports 214 and 216 open to two lines 283 and 284 leading respectively -to opposite ends of the cylinder bore 224 of the direction valve 220. The ports 280 and 211 arefconnected respectively to the exhaust line 259v and the line 202 leading to one end of the start and stop valve |16. The two remaining ports 218 andV 219 are connected through passages 285 and 286 to the rapid traverse valve 244.

'I'he rapidv traverse valve 244 (see Figs. 3, 12, 13, and 17) comprises avertical bore 281a opening vertically through the block 250 and closed by end plates 281. Nine annular ports 288 to 296 are formed in the bore 281e, and are controlled bya valve' piston 291 of thek spool type having an operating stem 298 extending'through the upper end plate 281. Three ports 288, 292, and 296 are connected to the exhaust line 258 and the remaining ports are connected respectively to the -pressure line |98, the lines 283 and 284 leading to the direction valve 220, the line 202 leading to one end of the Valve |16, and the lines 285 and 286. To provide means for actuating the valve 244, the upper end of the stern 298 is connected by an adjustable link 299 to a crank arm 300 on a rock shaft 30| journaled vin the housing 246. The shaft 30| extends through the cover plate 241 and is provided with a hand lever' 302. Also fixed on the shaft 30| is a segment'or lever 303 having teeth 304 adapted for selective engagement with a yieldable spring-actuated detent pin 305 to locate the valve piston 291 in intermediate' neutral position or in either end position.V The pin 305 is slidable'in a block 306 bolted to the top wall ofthe housing 246.

'Ihe feed control valve 243 is urged downwardly by a compression spring 301 into normal inoperative position, and is adapted to be elevated into operative position as hereinafter described. When the valve 243 is in inoperative position. and the rapid traverse'valve 244 is in neutral position, the control line 202 is connected through the ports 211 and 218, the line 285 and the ports 295 and 296 to the exhaust line 258, and all other lines leading to the valves are blocked by the pistons 28| and 291. When the valve 243 is elevated, the lines 259 and 260 are connected respectively to the lines 284 and 283 so as to effect actuation of the direction valve 229 in accordance with the adjustment of the valve 242. and the connection between the lines 202 and 285 is interrupted to condition the pump unit |35 for feed traverse, providing the rapid traverse valve 244 is in neutral position. The line 286 is now connected through the ports 219 and 280 to the exhaust line 258. If the rapid traverse valve 244 should be out of neutral position, the line .286 would be connected to the line 202 through the ports 293 and 294, thereby preventing feed traverse.

Movement of the rapid traverse valve 244 into the upper end position will connect the pilot lines 283 and 284 respectively to the pressure and exhaust lines |98 `and 258` and movement into the other end position will reverse these connections. In either operative adjustment, the connection between the lines 258 and 285 is interrupted, and a connection between the lines 202 and 286 is established so that the line 202 will be open to exhaust if the feed control valve 243 is not in inoperative position, thereby preventing rapid traverse. It will therefore be seen that the valves 243 and 244 are interlocked to prevent simultaneous control.

Control by either of the valves 243 and 244 is conditional on position of the work slide 1. The slide 1 is controlled by a starting valve 308 (see Figs. 3, 12, 13, 15, and 17) comprising a vertical bore 309 and a piston 3|0 of the spool type slidable therein. Formed in the bore 309 are nve annular ports, namely, two end ports 3|| and 3|2 connected to the exhaust line 258, a port 3|3 connected to the pressure line |98, and two ports 3| 4 and 3|5 connected respectively to lines 3|6 and 3 1 leading to opposite ends of the cylinder of the elevating motor 36. A coiled compression spring 3|8 tends to elevate the piston 3|0 into position to connect the lines 3|6 and 3|1 respectively to the lines |98 and 258 so as to elevate the Work slide 1. Upon lowering the piston 3|0, these connections are reversed to lower the work slide 1.

Interposed in the line 3|6 is a resistance valve 3|9 permitting a free ow to the lower end of the motor 36 but restricting the return ilow. The purpose of the valve 3|9 is to hold up the work slide 1 when the pump unit |35 is not in operation. The valve 3|9 (see Figs. 3 and 13) comprises a bore 320 having an annular port 32| connected to the starting valve 308 and an opening 322 connected to the motor 36. An annular valve seat 323 is tted in the bore 320 between the port 32| and the opening 322. Slidable in the bore 320 is a longitudinally iluted valve member 324 having an axial valve passage 325 with a ball seat 326 and radial passages 321 open to the port 32|. A ball 328 normally engages the seat 326 and prevents a return flow through the passage 325 to the port 32|. The valve member 324 is normally urged into engagement with the seat 323 by an adjustable compression spring 329 in the lower end of the bore 320. When the line 3 I6 is connected to exhaust, the fluid in the lower end of the motor 36 can escape through the valve 3|9 only by moving the valve member 324 from the seat 323 against the pressure of the spring 329. This pressure is suiicient to hold the work slide 1 in elevated position except when the upper end of the motor 36 is connected to pressure.

To permit lowering of the work slide 1 at will, a needle valve 330 is interposed in a by-pass across the lines -258 and 3|6 between the motor 36 'and the resistance valve 3| 9.

Thestarting valve piston 3|0 has an actuating stem 33| which projects upwardly from the bore 309, and which is connected by a link 332 to a crank arm 333 on a rock shaft 334 journaled in the housing 246. The shaft 334 extends through the cover 241 and is provided with a hand lever` 335. Detent means is provided for holding the piston 3|0 in lowered position to maintain the work slide 1 in operative position, and this means comprises a spring-actuated pawl 336 Vpivotal in a lug 331 on the valve block 250, and adapted automatically to-engage an annular ratchet groove 338 in the stem 33|.

The line 3|1 to the upper end of the motor 36 has a branch connected through a resistance valve 339 to a line 340 leading to the lower end of the bore 210 of the feed controlvalve 243. This valve is similar in construction to the valve 3|9, and will pass uid to the line 340 when the pressure in the line 3|1 rises above a predetermined amount, as it will after the work slide 1 has come to rest in operative position. 'Upon the supply of fluid to the line 3|1, the valve piston 28| will be elevated hydraulically into operative by a manual two-way valve 344 to a line 345 connected in common to all the clamp cylinders 62. The valve 344 is operable by a hand lever 346 on the front of the slide 1, and serves in one position to connect the lines 340 and 345 and in the other position to connect the line 345 to the exhaust line 258. Hence the valve 344 affords means for releasing and applying the clamps 4| at will when the slide 1 is held in lowered position.

Mounted on the column 5 for operation by the work slide 1 is a valve 341 controlling the feed clutches |44 and |5|, and preventing the hydraulic system from being conditioned for rapid traverse unless the slide is in elevated position. The valve 341 comprises a vertical casing 348 having a bore 349 closed at opposite ends by suitable plates 350 and A plurality of annular ports 352 to 358 are formed in the bore 349, and are controlled by a piston 359 of the spool type having an actuating stem 360 extending through the plate 350. The upper end of the bore 349 and the port 355 are connected to the exhaust line 258, and the port 358 is adapted to be connected to the line 258 by a safety valve 36| when the work and tool spindles and 22 are not in operation. The ports 353, 356 and 351 are connected respectively to the lines |98, 203 and 202. Two lines 362 and 363 open from the closed ends of the clutch cylinders |51 and |58 respectively to the remaining two ports 354 and 352.

A coil compression spring 364 in the lower end of the bore 349 normally holds the piston 359 in elevated position. In this position, the line 203 is blocked to condition the valve |16 for rapid traverse, the lines 362 and 363 are connected respectively to the pressure and exhaust lines |98 and 258, and the line 202 is blocked, 'subject to connection through the valve 243 or the valve 244 to exhaust. As a result, the feed clutch .|5I is open and the rapid traverse clutch |44 is closed; also, the rapid traverse valve 244 is operative.

As the work slide 1. is lowered into operative position, a dog 365 movable therewith engages the upper end of the stem 360 and depresses the valve piston 359. The dog 365 is adjustably mounted on a rod 366 clamped to the slide 1.

When the slide 1 reaches operative position, 'a

pawl 361 pivoted on the plate 358 engages releasably in an annular ratchet groove 368 in the stem 360 to hold the piston 359 in lowered position. A dog 369 adjustably mounted on the rod 366 is operable to release the pawl 361 upon elevation of the slide 1 back into inoperative position. In the lowered position of the valve 341, the connections to the lines 362 and 363 are reversed to close the feed clutch |5| and open the rapid traverse clutch |44, and the line 203- is connected to the exhaust On exhaust, the fluid will line 258 to disable the rapid traverse valve 244. This valve 244 is now available asa manual feed control valve if the automatic cycle is not desired. The line 202 is connected to the port 351 so that the valve |16 will not be conditioned for feed unless the spindles and 22 are rotating.

The safety valve 36| (see Figs. 3 and 7) has a casing 318 mounted on the bracket 90, and` formed with ports 31| and 312 connected respectively to the exhaust line 258 and through a line 313 to the port 359 in the valve 341. A piston 314 is slidable in the casing 310, and is connected through a rod 31.5 and a yoke 316 to a sleeve 311 of a centrifugal governor 318 rotatable with the shaft 16 in the spindle drive. When the shaft 16 is idle, the piston 314 is positioned to connect the ports 31| and 312.

to block the port 312.

Operable withthe starting valve 308 is a valve 319 for controlling Vthe clutch 15 in the spindle drive. The valve 319 (see Figs. 3, 15, 17 and 18) comprises a vertical bore 38,0 opening through the block 258 and closed at opposite ends.

exhaust line 258. Two ports 38| and 382 are formed in the bore 380, and connected respectively to the pressure line |98 and the linev 92 leading to the clutch cylinder 85. A piston 383 is slid#- able in the bore 380, and has a stem 384 adapted for end engagement by an arm 385 on the shaft 334. A Spring 386 tends to elevate the piston 383 so as to connect the line 92 to exhaust. When the piston 383 is depressed, the clutch cylinder is connected to the pressure line |98.

The valve is also manually operable independently of the cycle valve 308, and to this end the stem 384 is formed in one side with a transverse notch 381. An arm 388 fixed on a rock shaft 389 journaled in the cover 241 extends into the notch 381 for engagement with the bottom side thereof. A hand lever 390 is iixed onthe outer end of the shaft 389 and carries a spring-actuated detent pin 39! adapted to enter selectively either of two recesses 392 in the cover 241..

The feed control valve 243 and the cycle valve 398 are subjected to automatic control in response to movements of the tool slide |1. means comprises a cam block 393 guided by slidingadjustment on the block 306, and adjustably secured, as by a set screw 394, to a rod 395 extending slidably through the housing 246. One end of the'rod 395 extends slidably through a lug 396 on the slide 1. Two spaced dogs 391 and 398 are adjustably secured on the rod 395 for engagement by the lug 396 upon movement of the slide |1 respectively into opposite limit positions. A stop collar 399 is slidable on the rod 395 for end engagement with the cam block 393, and is secured to the inner end of a rod A480 extending through the side wall of the housing 246. Lock nuts 40| on the outer end of the rod 400 limit the inward position of the vcollar 399. Also slidable on the rodl395 and extending slidably through a bearing 482 in the side wall of the housing 246 is an elongated sleeve 403 having inner and outer end flanges 494 and 465. A coiled compression spring486 encircles the rod 395 and abut-s at opposite ends against the collar 399 and the flange 464.l The spring 496 tends to'urge the collar 399'into its innermost position and the flange 404 against the bearing 492 to locate the cam lock 393 in neutral position. A collar 401xed on the rod 395 'engages Vthe outer flange 405v of the sleeve 403. When the lug 398 engages the Uponk rotation of the shaft 16, the piston 314 will move into position` OD- v posite ends-of the bore 380 are connected to the The controlY dog 398, the cam block 393 is moved to the right out of neutral position and acts against the collar 399 to compress the spring 406. Conversely, when the lug 396 engages the dog 391, the cam block 393 is moved to the left out of neutral position, and the sleeve 403 compresses the spring 406. Thus, in each instance, spring pressure is stored up to return the cam block 393 automatically to neutral position when the lug 396`releases the rod 395.

The cam block 393 is formed to provide selectively either a conventional cycle in which the slide I1 is fed to left and returned rapidly to the right, or a climb cutting cycle in which the feed and rapid traverse movements are reversed. More particularly, the cam block 393 is formed in the bottom along the rear with two cam recesses 408 and 409 and along the front with two cam recesses 4|0 and 4| I. The recesses 408 and 4|0 are adapted for selective engagement with a roller 4I2 on an arm 4|3 fixed on a shaft 4|4 extending slidably and rotatably through the housing 246. Also fixed on the shaft 4|4 is an arm 4|5 adapted for engagement with the pawl 34| to release thefeed control valve 243. A hand knob 4 I 6 on the front end of the shaft 4 I 4 affords means for shifting the roller 4|2 selectively into the path of one or the other of the recesses 408 and 4|0, spring detent means 4|1 being provided for holding the shaft yieldably in position of adjustment. Similarly, the recesses 409 and 4|| are adapted for engagement with a roller 4|8 on an arm 4|9 xed on a rock shaft 420. This shaft extends slidably through the housing 246 to the front of the cover 241, and is provided with a disengaging lever 42| whereby the roller 4I8 may be positioned for engagement with one or the other of the recesses 409 and 4| I, and whereby the shaft may be rocked manually. A second arm 422 on the shaft 420 is adapted for engagement with the pawl 336 to release the starting or cycle valve 308.

When both shafts 4|4 and 420 are adjusted inwardly, the control is conditioned for an automatic conventional cycle comprising feed to the left, automatic reversal and rapid traverse to the right. In this instance, the cam recess 409 will engage the roller 4|8 at the end of the feed to trip the cycle valve 308 as a result of which the slide 1 will be elevated to trip the valve 341, thereby blocking the line 203 and closing the clutch |44 for rapid traverse in the reverse direction. At the end of the return, the cam recess 408 will engage the roller 4|2 to trip the feed control valve 243 and thereby stop the slide |1. If it is desired to stop the slide |1 at the end of the feed, the shaft 4|4 is pulled out so that the cam recess 4I0 will engage the roller 4|2 to release the feed valve 243 before the cam recess 409 engages the roller 4|8 to trip the valve 308. When both shafts 4|4 and 420 are pulled out, the cam recess 4|| will trip the valve 308 at the end of the feed to the right and the recess 4|0 will trip the valve 243 at the end of the rapid traverse to the left. In this cycle, adjustment of the shaft 4| 4 inwardly will cause the slide |1 to stop at the end of the feed.

Means is provided for moving the manual rapid traverse valve 244 automatically into neutral position if it is in either end position upon movement of the slide l1 into either limit position. This means comprises two spaced lugs 423 and 424 on the side of the cam block 393, and adapted for engagement respectively with opposite sides of a roller 425 on the arm 303 to center the latter upon movement'of the block out of neutral position. The lugs 423 and 424 however are suitably spaced to permit free actuation of the valve 244 at all other times.

Mounted in the housing 246 is a limit switch 426 for a coolant motor (not shown) The switch 426 has an operating shaft 421 with a lever arm 428 carrying a roller 429 on the free end. Slidablyand rotatably adjustable in the housing 246 is a rock shaft 430 carrying a wide arm 43| underlying a roller 432 on the arm 333. The arm 43| is shiftable into and out of position over the roller '429. The shaft 430 is provided with a hand knob 433 to facilitate this adjustment, and is held releasably in position of adjustment by a spring detent 434. It will be evident that, when the arm 43|' is located between the rollers 429 and 432, actuation of the clutch valve 319 to start the spindles and 22 will result in closing the switch 426 to start the coolant flow. When the spindles are stopped, the coolant supply will stop.

I claim as my invention:

1. A hobbing machine comprising, in combination, a base having a vertical column, a first slide vertically movable on said column either into elevatedinoperative position or lowered operative position, a horizontal spindle on said slide, a second slide reciprocable on said base axially of said spindle, a spindle on said second slide, means for rotating said spindles in timed relation, hydraulic means for moving said first "slide into operative position, and hydraulic means automatically operable upon movement of said rst slide into operative position to move said second slide through a feeding stroke in one direction, said first hydraulic means being automatically operable at the end of said feeding stroke to return said first slide into inoperative position.

2. A hobbing machine comprising, in combination, a. base having a vertical column, a first slide vertically movable on said column either into elevated inoperative position or lowered operative position, a horizontal spindle on said slide, a second slide reciprocable on said base axially of said spindle from initial position in a forward direction and then in a reverse direction, a spindle on said second slide, means for rotating said spindles in timed relation, and hydraulic means automatically operable upon the return of said first slide into inoperative position to return said second slide at a rapid traverse rate in said reverse direction into initial position.

3. A hobbing machine comprising, in combination, a base having a vertical column, a first slide vertically movable on said column either into elevated inoperative position or lowered operative position, a horizontal spindle on said slide, a second slide reciprocable on said base axially of said spindle, a spindle on said second slide, means for rotating said spindles in timed relation, manually controllable hydraulic means for traversing said second slide at a rapid trav-V erse rate in either direction when said first slide is in inoperative position, and being inoperable when said first slide is in operative position, and hydraulic means automatically operable upon movement of said rst slide into operative position to move said second slide at a feeding rate. 4. A hobbing machine comprising, in combination, a base, a irst spindle mounted on said base, a second spindle mounted on said base for translation into and out of operative position relative to said rst spindle, and means automatically operable upon movement of said second spindle into operative position to clamp said second spindle in such operative position.

5. A hobbing machine comprising, in combination, a base, a spindle supported on said base, a slide mounted on said base for movement axially of said spindle, a spindle supported on said slide, means for rotating said spindles in timed relation, means for translating said slide, and means for rendering said last mentioned means inoperable unless both spindles are rotating.

6. In a machine tool, in combination, a base having a column with vertical parallel spaced ways, a slide mounted for reciprocation on said ways, adjustable means for limiting the upper and lower end positions of said slide, a lhydraulic motor for elevating and lowering said slide,a fluid supply line, an exhaust line, valve means for connecting said lines alternately vand reversibly to opposite ends of said motor, a second slide mounted for horizontal reciprocation on said base, a second hydraulic motor for translating said second slide, valve means normally in inlically into operative position to control said second motor, a branch line leading from the upper end of said rst motor to said valve to supply valve actuating fluid, and a'resistance valve interposed in said branch line whereby said valve will be actuated t'o start said second motor upon movement of said first slide into its lowermost position.

7. In a machine tool comprising, in combination, a base, a column on said base, a first slide reciprocable on said column, a spindle journaled in said slide, a second slide reciprocable on said base axially of said spindle, a spindle journaled in said second slide, means for driving said spindles, a stop abutment on said base, a stop abutment on said column, a vertical stop screw adjustably mounted on said rst slide and adapted for engagement selectively with said stop abutments to define respectively an elevated inoperative position and a lowered operative position, means for adjusting said screw axially on said slide, means for locking said screw in position of adjustment, and means for elevating and lowering said first slide.

8. In a machine tool comprising, in combination, a base, a column on said base, a first slide reciprocable on said column, a spindle journaled in said slide, a second slide reciprocable on said base axially of said spindle, a spindle journaled lowered operative-position relative to said secondy slide, and means for elevating and lowering'said first slide.

9. In a machine tool comprising, in'combination, a base, a column on said base, a first slide re'- ciprocable on saidA column, a spindle journaled` in said slide, a secondslide reciprocable on said base axially of said spindle, a spindle journaled 10. In a machine tool comprising, in combination, a base, a column on said base, a first slide reciprocable on said column, a spindle journaled in said slide, a second slide reciprocable on said base axially of said spindle, a spindle journaled in said second slide, means for driving said spindles, a stop abutment on said base, a stop adjustably mounted on said first slide and adapted for engagement with said stop abutment to define a lowered position relativeV to said second slide, a vertical piston and cylinder motor for elevating and lowering said first slide, and hydraulic means for supplying pressure iluid reversibly to` opposite ends of said motor and including valve means for hydraulically blocking the lower end of said motor to support said second slide in elevated position upon failure of fluid supply.

11. In a machine tool, in combination, a base having a vertical column, a spindle slide reciprocable on saidcolumn, a hydraulic motor for elevating and lowering said slide and having upper and lower uid supply lines opening to opposite ends, a pressure fluid supply line, an exhaust line, valve means for connecting said supply lines reversibly to said pressure and exhaust lines, a resistance valve interposed in the lower supply line for permitting the passage of-fluid freely tothe lower end of said motor, a needle valve selectively available to connect the lower end of said motor to said exhaust line, a spindle slide on said base,` and means for translating said last mentioned slide, said valve means being adapted to be latched in position to direct pressure iluid to the upper end of said cylinder and to be automatically released for movement into position to direct fluid to the lower end of said cylinder upon movement of said last mentioned slide into a predetermined position. i

12. In a machine tool, in combination, a base having a vertical column, a spindle slide reciprocable on said column, a hydraulic motor for elevating and lowering said slide and having upper and lower fluid supply lines opening to opposite ends, a pressure fluid supply line, an exhaust line, valve means for connecting said supply lines reversi-bly to said pressure and exhaustlines, 'a spindle slide on said base, and means for translating said last mentioned slide, said valve means being adapted to be latched in positionto direct pressure iiuid to the upperv end of said cylinder and to be automatically released for movement into position to direct fluid to the lower end of said cylinder upon movement of said last mentioned slide into a predetermined position.

13. In a machine tool, in combination, a base having a vertical column, a slide reciprocable on said base, a spindle journaled in saidslide, means including a normally open clutch for driving said spindle, a hydraulic motor for closing said clutch, a second slide reciprocable on said base axially of said spindle, a hydraulic transmission for reciprocating said second slide and including a stop valve having a control line adapted upon connection to exhaust to effect adjustment of said valve into stop position, a valve mounted on'said column and automaticallyV operable'upon movement of said rst slide into lowered position-to disable said transmission for rapid traverse oper-V ation and upon'movementV of the slide into elevated position to condition said transmission for' rapid traverse operation and being operable when said slide is in s'aid lowermost position to'connect said control line to exhaust, and a safety valve interposed in said control line and automatically operable independently of said second mentioned valve to close said control line to condition said stop valve for operation upon rotation of said spindle.

14. In a machine tool, comprising, in combination, a base having a vertical column, a first slide reciprocable on said base, a spindle journaled in said slide, a second slide reciprocable on said base axially of saidspindle, a spindle journaled in said second slide, means for driving said spindle in positive timed relation including a differential mechanism, hydraulic means for elevating and lowering said rst slide selectively into an inoperative position and a lowered operative position, a, selective rapid traverse and feed mechanical transmission for translating said second slide and for driving said differential mechanism in timed relation to the movement of said second slide, hydraulic means for operating said mechanical transmission, and valve means for controlling both said hydraulic means, and including valve means operable by said first slide to adjust said mechanical transmission for feed in one direction upon movement of said first slide into operative position and for rapid traverse in a reverse direction upon movement of said first slide into inoperative position. y

15. A hobbing machine comprising, in combination, a support, a rst slide movable on said support either into inoperative position or operative position, a spindle on said slide, a second slide reciprocable on said support axially of said -spindle, a spindle on said second slide, means for rotating said spindles in timed relation, hydraulic means for moving said first slide into operative position, and hydraulic means automatically operable upon movement of said first slide into operative position to move said second slide through a feeding stroke in one direction, said rst hydraulic means being automatically operable at the end of said feeding stroke to return said first slide into inoperative position.

16. A hobbingmachine comprising, in combination, a support, a rst slide movable on said support either into inoperative position or operative position, a spindle on said slide, a second slide reciprocable on said support axially of said spindle, a spindle on said second slide, means for rotating said spindles in timed relation, manually controllable hydraulic 'means for traversing said second slide at a rapid traverse rate in either direction When said first slide is in inoperative position, and being inoperable when said rst slide is in operative position, and hydraulic means automatically operable upon movement of said rst slide into operative position to move said second slide at a feeding rate.

17. In a machine tool comprising, in combina` ially on said slide, means for locking said screw in position of adjustment, and means for reciprocating said first slide.

18. In a machine tool comprising, in combina tion, a support, a first slide reciprocable on said support, a spindle journaled in said slide, a second slide reciprocable on said support axially of said spindle, a spindle journaled in said second slide, means for driving said spindles, a stop abutment on said support, a, stop adjustably mounted on said first slide and adapted for engagement with said stop abutment to dene an operative position relative to said second slide, and hydraulic means for reciprocating said rst slide.

19. A hobbing machine comprising, in combination, a rst spindle and a support therefor, a second spindle reciprocable axially of said first spindle, and a combination mechanical and hydraulic transmission for translating said second spindle, said transmission including cycle control means selectively adjustable to obtain either an automatic cycle comprising a feeding movement in one direction, an automatic reversal at the end of said feeding movement, an automatic rapid traverse return movement in the other direction, and an automatic stop at the end of said return movement, or a reverse automatic cycle comprising a feeding movement in said other direction, an automatic stop at the end of said last mentioned feeding movement, an automatic rapid traverse return movement in said one direction, and an automatic stop at the end of said last mentioned return movement.

20. A hobbing machine comprising, in combination, a base, a rst spindle mounted on said base, a second spindle mounted on said base for translation into and out of operative position relative to said rst spindle, means automatically operableV upon movement of said second spindle into operative position to clamp said second spindle in position of adjustment, and means automatically operable upon movement of said second spindle into operative position to translatel said first spindle relative to said second spindle.

21. A hobbing machine comprising, in combination, a support, a first slide movable on said support either into inoperative position or operative position, a spindle on said slide, a second slide reciprocable on said support axially of said spindle, a spindle on said second slide, means for rotating said spindles in timed relation, drive means for moving said first slide into operative position, and drive means automatically operable upon movement of said first slide into operative position to move said second slide through a feeding stroke in one direction, said rst drive means being automatically operable at the end of said feeding stroke to return said first slide into inoperative position. Y

22'. A hobbing machine comprising, in combination, a support, a first slide movable on said support either into inoperative position or operative position, a spindle on said slide, a second slidereciprocable on said support axially of said spindle, a spindle on said second slide, means for rotating said spindles in timed relation, manually controllable means for traversing said second slide at a rapid traverse rate in either direction when `said iirst slide is in inoperative position, and being inoperable when said first slide is in operative position, and drive means automatically operable upon movement of said first slide into operative position to move said second slide at a feeding rate.

BENJAMIN R. PURVIN. 

